1. Field of the Invention
This invention relates to a pneumatic tire comprising a carcass formed by putting cords to an outside of a support and a method of building the same.
2. Description of Related Art
As the pneumatic tire comprising a carcass formed by putting cords to an outside of a support, there has hitherto been known a tire described, for example, in JP-A-6-171306. In such a tire, the carcass is comprised of a cord toroidally extending between a pair of bead portions in a meridional direction, which consists of many arch portions arranged over a full circumference of the tire so as to separate away from each other at a constant pitch C in a center of the tread in the circumferential direction, and many circumferential portions alternately connecting radially inward ends of the adjacent arch portions located in both bead portions to each other and extending substantially in the circumferential direction. In order to anchor the cord of the carcass in the bead portion, inner and outer bead layers are formed by spirally winding a bead cord plural times at the outside and inside of the circumferential portion in the axial direction of the tire in the vicinity of the radially inward end of the arch portion, respectively. A high-hardness rubber layer is arranged between the inner bead layer and the carcass and between the outer bead layer and the carcass to join the inner and outer bead layers to each other, whereby it is prevented to get out the circumferential portion of the carcass outward in the radial direction of the tire.
In the conventional pneumatic tire, however, there is a problem that since each of the circumferential portions is made from a single fine cord, even if the high-hardness rubber layer is arranged between the carcass and the inner bead layer and between the carcass and the outer bead layer as mentioned above, the getting out of the circumferential portion can not sufficiently be prevented. Also, the distance in the circumferential direction between the arch portions constituting the carcass or a constant pitch C is narrow, so that it is difficult to conduct the putting work of the cord.